Articles & Case Studies


Posted: Monday 6th July 2020

Normal 0 false false false EN-US X-NONE X-NONE Veolia Water Technologies UK (VWT UK) has delivered new Moving Bed Biofilm Reactor (MBBR) plants to five Severn Trent sites, allowing all to achieve tighter ammonia discharge consents as required by the Water Framework Directive.

Severn Trent, and its main contractors nmcm and Mott MacDonald Bentley (MMB) were looking to upgrade an existing asset at one site in Hodsock and install four new build tertiary plants at four other Severn Trent sites – Boughton, Lichfield, Trescott and Little Aston. Four of the five plants required a solution that would produce an ammonia consent of less than 1mg/l as a 95th percentile.

Severn Trent and its contractors approached VWT UK to design a bespoke solution for the sites, due to VWT UK’s history in pioneering MBBR technology solutions over the last 30 years.

A new patented configuration of Veolia’s AnoxKaldnes™ MBBR technology was developed, to achieve the required low ammonia discharge consents whilst also combating any spikes in ammonia load that may be received by the plants.

An aerobic wastewater treatment method, MBBR systems use active biofilm carriers made from plastic with large surface areas on which bacteria can grow with optimal culture conditions. The carriers are kept constantly in motion using aeration allowing the bacteria to break down organic material in the wastewater. MBBR systems are particularly efficient at the removal of biochemical oxygen demand (BOD), ammonia and nitrogen. The large surface area of the carriers in the AnoxKaldnes™ patented MBBR systems enable the treatment of a high quantity of wastewater using a very small footprint.

This development has enabled VWT UK, with the help of the contractors, to save significant levels of capital expenditure for Severn Trent Water by providing a small footprint solution that enabled the existing treatment process to be upgraded rather than replaced.

Lance Mott, Contracts Manager – Water at nmcm, one of the main contractors on the project commented: “Having supervised the installation process at Boughton and Lichfield, I am happy to say that it has worked exceptionally well and is exceeding everyone's expectations. Severn Trent Water was initially looking for an activated sludge plant (ASP) but after successful cost benefit analysis and stakeholder management we had Severn Trent Water’s approval to use VWT UK’s MBBR plant which was our preference.

“The process plant on Boughton has been running now for over 18 months, saving Severn Trent £250,000 per year associated with the spring sloughing during temperature and seasonal changes, with the MBBR maintaining a stable biofilm. The plant is removing nearly all the ammonia (NH3) from the wastewater - from the original design criteria of 1.2mg/l it is actually now working at 0.01mg/l. We have witnessed the same results at the Lichfield plant, with the existing works previously operating to meet its consent of 17mg/l of NH3. Since the plant has been in operation it is now meeting 1.5mg/l of NH3 and it is still not fully matured.”

Work is now complete on all five sites and the plants are now in beneficial use.

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August 2021

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